The present invention relates to a polymerization apparatus including a radiation source for emitting radiation for inducing polymerization, especially radiation in the form of light, into a first chamber, comprising a flexible radioparent membrane or diaphragm that separates the second chamber from a first chamber, whereby into the second chamber a model to be subjected to radiation is placed, especially a tooth stump, and whereby between the model and the membrane a foil is provided. The membrane, with the aid of a differential pressure, is deflected into the second chamber toward the model in order to deform the foil about the model.
Such a polymerization apparatus is known from International Patent Application WO 95/08300. In this polymerization apparatus a piece of pre-impregnated matrix material is placed onto a tooth stump or another model The term model in the context of the present invention refers to positive molds as well as negative molds.
Due to the differential pressure between the two chambers in the apparatus, a soft and flexible diaphragm positioned in the apparatus is forced onto the model (mold) so that the foil is pressed onto the model and is shaped according to the contour of the model.
A problem of such polymerization apparatus is ensuring a precise and reliable polymerization by light curing. Especially in the case of dental replacement parts, it is imperative that complete curing takes place whereby complete curing must be ensured within a limited amount of time. Thus, in general, output-intensive light sources (high luminous power) with corresponding spectra are used. For thermal as well as energetic reasons, the light electrical power usage should not be too great especially since high light intensity light sources are comparatively expensive to replace on a regular basis when spent.
In the apparatus known from the aforementioned application the light radiation must penetrate the flexible diaphragm and this results in certain losses of luminous power. Furthermore, the distance between the tooth stump and the light source must be selected such that for all model sizes occurring in practice sufficient space is provided. On the other hand, the luminous power is reduced more than proportionally with increasing distance so that measures for increasing luminous power have become known.
These measures include, for example, the teaching disclosed but not discussed in detail in the aforementioned publication. For improving the reflection of light beams within the area of the radiation source special reflectors in the form of an annular mirror 19 that fills the entire model chamber are provided.
The cycle times for the actual light curing process is determined substantially by how fast the required vacuum can be generated within the model chamber.
For the deformation of the foil which must adhere to the contour of the model, the application of a uniform high force is required which in practice is realized by a corresponding pressure differential. This pressure differential in connection with partly rugged or fissured models result in a considerable stress load of the flexible diaphragm. The diaphragm must therefore be exchanged quite frequently for safety reasons because a small hole or crack within the diaphragm would have disadvantageous results in regard to the molding process.
It is therefore an object of the present invention to provide a polymerization apparatus of the aforementioned kind with which the light output as well as the service life of the diaphragm can be improved.